They are the titular characters of the upcoming 20th Century Fox film that has received an avalanche of free publicity in recent weeks because of widely circulating rumours that the Pitt-Aniston marriage was affected by an alleged on-set romance between Pitt and his Smith co-star, Angelina Jolie. In the movie, the actors play married assassins assigned to kill each other.

Regardless of the questionable veracity of these unsubstantiated rumours, they pose an unusual dilemma for Fox and studio-based producer Regency Enterprises: How will the attention Smith is getting affect its box office prospects'

It's a question being internally debated at the studio and in the film industry at large, especially in light of how actors' romances ' real or imagined ' that might sizzle offscreen often fizzle at the box office. Fox has scheduled the movie's release for June 10, in the heat of the summer box office battles.

Sources close to the production and inside Fox say Smith is benefiting from the attention. 'This is like hitting the jackpot,' one studio source confided.

But a rival studio executive, who declined to be identified, countered that the media maelstrom will be challenging. 'The people at Fox are probably just dying right now, trying to figure out what the next steps are,' the executive said. 'Because they are going to have to keep the press focused on Smith and not on who broke up whom.'

A spokesperson for Regency said there are no plans to deviate from pre-separation promotional strategy: 'None of the marketing going forward has anything to do with any gossipy back story, nor will it. It's all about the movie.'

Less than a month ago, Smith was just another summer action thriller, albeit flying lower on the radar than such tentpole projects as Steven Spielberg's War of the Worlds or Fox's Fantastic Four. But awareness for Smith began to skyrocket January 7, when the announcement of the Pitt-Aniston split was accompanied by a barrage of thinly sourced speculation alleging that Pitt and Jolie were unusually chummy on the set of Smith, which was filmed in Rome, New York and Los Angeles.

The frenzy is reminiscent of the one that enveloped star-crossed couple Jennifer Lopez and Ben Affleck, whose brief engagement played out in public last year. Ryan Moore, vice-president at entertainment marketing firm Set Resources, sees a connection between their over-exposure and the dismal reception of their films Gigli and Jersey Girl.

'The overkill of 'Bennifer' was really extreme by that point,' he said, cautioning that the Pitt-Jolie story could hurt Smith if it lasts too long.

Hollywood has a rich tradition of real-life love affairs that carry over onto the silver screen. Reports of an extramarital dalliance between Elizabeth Taylor and Richard Burton helped fuel interest in their expensive 1963 epic, Cleopatra, which also was distributed by Fox.

Arguably, the case that most closely resembles Smith is that of the poorly received 2000 film Proof of Life. An on-set relationship between stars Russell Crowe and Meg Ryan, who subsequently ended her marriage to Dennis Quaid, proved so distracting in the film that its director, Taylor Hackford, reportedly removed some love scenes in a futile attempt to keep viewers from blurring fiction with reality.

Conventional wisdom has it that in an age when every celebrity is overexposed, star couples quite literally leave nothing to the imagination when they collaborate on film. If so, that could present a golden opportunity for Smith: The very fact that the alleged relationship between Pitt and Jolie is shrouded in mystery might draw curious viewers to theatres to suss out whether their onscreen chemistry reveals the offscreen truth.

The did-they-or-didn't-they drama could very well play itself out in the marketing of the film, said Gitesh Pandya, editor of industry tracking website BoxOfficeGuru.com.

In their current form, the promotional material for Smith plays down the intimate scenes between its stars. Pitt and Jolie make no physical contact in the posters currently up in select theatre lobbies, and the trailer barely crams in a few seconds of sensuality between the explosions and gunplay.

Pandya believes the exposure will help Smith attract gossip-consuming teenagers. But he thinks the hoopla over Pitt and Jolie will be a faint memory in the rapid-cycle celebrity news culture by the time the film's release rolls around. 'The coverage will subside before it picks again when the movie is released,' he predicted.